A semiconductor memory device stores data through a write operation, and outputs stored data through a read operation. When a write or read operation is performed, data inputted to or outputted from the semiconductor memory device is gradually attenuated by line loading of a data line. When the data is severely attenuated, the data may be distorted. Therefore, a circuit is required to restore the attenuated data. Therefore, the semiconductor memory device includes a sense amplifier circuit to sense and amplify the data transmitted through the data line and transmit the amplified data to another data line.
The sense amplifier circuit used in the semiconductor memory device may include an input/output sense amplifier (IOSA). In general, the IOSA is implemented as a cross-coupled latch type and configured to sense and amplify data transmitted through an input data line and transmit the amplified data to an output data line. The data transmission operation of the IOSA is performed during an enable period set by an enable signal. The enable period is set to a pulse width of the enable signal, that is, a period in which the enable signal is at logic high level (or logic low level depending on embodiments).
However, the pulse width of the enable signal for controlling the operation of the IOSA is constant regardless of a swing width of data transmitted through the input data line. Therefore, a problem may occur in timing margin and current consumption. That is, as the swing width of the data transmitted through the input data line decreases, a time required for turning on PMOS and NMOS transistors included in the IOSA increases. Therefore, it is difficult to sufficiently secure a timing margin for transmitting data from the input data line to the output data line. The insufficiency of the timing margin becomes more severe during high-speed operation. Furthermore, as the swing width of the data transmitted through the input data line increases, the time required for turning on the PMOS and NMOS transistors included in the IOSA decreases. Therefore, even after the data is transmitted from the input data line to the output data line, the operation of the IOSA continues to cause current consumption.